You want to change the tracker URL or Passkey for all torrents of a tracker? Below the method I applied. The commands are based on a setup matching http://dev.deluge-torrent.org/wiki/UserGuide/Service/systemd, adapts to your setup if needed. The example shows a tracker URL change but the passkey can be changed by the same method

OLD_TRACKER_URL and NEW_TRACKER_URL represent variable you have to change depending your tracker